Species

Dianella caeruleaBlue Flax-Lily

3 other cultivars

grass

Blue Flax-Lily

Dianella caerulea 'Cassa Blue'

The Story

Plant Bio

Dianella caerulea is a tufted, evergreen perennial native to eastern Australia, characterized by its clumping habit and strappy, linear foliage. In spring, it produces delicate panicles of blue to violet flowers with prominent yellow stamens, followed by glossy, purple-blue berries in summer.

'Cassa Blue' is a compact, dwarf selection distinguished by its stiff, upright growth habit and rich blue-grey foliage that intensifies in color during cold winter conditions. Unlike some wild forms, this cultivar does not spread aggressively via wide underground rhizomes, maintaining a tidy clumping form.

Uses & Benefits:

Provides year-round architectural structure with its stiff, upright, blue-grey foliage and decorative summer berries.

Offers exceptional drought tolerance and wind resistance, making it highly effective for coastal erosion control and low-water landscaping.

Attracts local insect pollinators with its spring flowers and provides food for songbirds that eat the berries.

SpeciesDianella caeruleaBlue Flax-Lily

Essentials

At a Glance

Plant Type

Grass

Height

18"

Width

16"

Light

Full Sun, Partial Sun

Zones

8, 9, 10

Water

Low

Humidity

High

Lifespan

Perennial

Native To

Australia

Toxicity

Toxic if ingested

Bloom period

Spring – Early summer

In flower about 4 months of the year

Planting

How to Grow

Select a planting site in full sun to partial shade with highly permeable, well-drained soil.
Dig a hole twice as wide as the root ball and of equal depth, amending heavy soils with coarse sand or planting on a raised mound to prevent waterlogging.
Gently loosen the outer roots of the container-grown plant and set it in the hole, ensuring the crown sits slightly above the surrounding soil level.
Water thoroughly at planting and maintain moderate moisture until the root system is established, after which irrigation can be significantly reduced.

Pro Tip

Plant in elevated mounds or slopes when dealing with heavy clay to ensure rapid drainage, and never shear the foliage flat like turfgrass, as the crown cannot regenerate from hacked woody stubble.

Keep It Thriving

Care Guide

Do

Plant on a slope or raised mound if your garden has heavy clay soil.
Apply a balanced or native low-phosphorus slow-release fertilizer once in spring.
Wear gloves when handling or pruning to avoid potential skin irritation from the sap.

Don't

Do not plant in low-lying, poorly drained areas where water pools after rain.
Do not shear or scalp the plant flat, as it does not regenerate well from hacked woody stubble.
Do not allow pets or children to ingest the ornamental blue berries, which contain toxic saponins.

Seasonal Care Calendar

Task	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Fertilize
Pest Check
Prune
Spring Cleanup

Watch Out For

Pests & Diseases

Common Pests

Common Diseases

In the Garden

Landscape Uses & Companions

Landscape Uses

Border EdgingMass PlantingRock GardensCoastal GardensContainer Thriller

Companion Plants

Festuca glauca Carex testacea Rosmarinus officinalis Lantana camara

Multiply

Propagation Methods

Good to Know

Common Questions

Blue Flax-Lily questions

What zones can Blue Flax-Lily grow in?

Blue Flax-Lily is hardy in USDA Zones 8–10. Inside that range it survives winter in the ground; outside it, grow it as an annual or a container plant you protect.

Is Blue Flax-Lily deer resistant?

Yes — Blue Flax-Lily is rated deer-resistant. Deer typically pass it over, though extreme hunger can override any plant's defenses.

When does Blue Flax-Lily bloom?

Blue Flax-Lily typically blooms in spring through early summer. Exact timing shifts a week or two with your zone — Sow's bloom calendar maps it to your garden.

Does Blue Flax-Lily need full sun?

Blue Flax-Lily does best in full sun to part shade. In hot climates, afternoon shade keeps blooms fresher longer.

Is Blue Flax-Lily drought tolerant?

Yes — once established (usually after the first full season), Blue Flax-Lily handles dry spells with minimal watering. Water deeply its first year to build the root system that makes that possible.